Highly shrinkable polyamide fibres



Sept. 1, 1910 Filed Nov. 15, 1966 United States Patent 015cc 3,526,571 HIGHLY SHRINKABLE POLYAMIDE FIBRES Fumimaro Ogata, Nishinomiya, Japan, assignor to Kanegafuclii Boseki Kabushiki Kaisha Filed Nov. 15, 1966, Ser. No. 594,496 Claims priority, application Japan, Dec. 1, 1965, 40/ 74,166 Int. Cl. D02g 3/00 U.S. Cl. 161-175 3 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to an improved highly shrinkable polyamide fibre in which a copolyamide having a high thermal shrinkability is arranged in the core portion and a homopolyamide is concentrically arranged in the surrounding portion and method of producing said fibres.

It is known that highly shrinkable polyamide fibres have heretofore been produced from suitable copolyamides.

However, highly shrinkable fibres formed of these conventional copolyamides, still have numerous drawbacks. For example, when it is desired to obtain fibres by using a copolyamide containing a large amount of copolymerizable component with the view to increasing shrinkability extremely, the crystallizability of saidcopolyamide is considerably decreased, resulting in troubles such as sticking and cohesion by fusion between the fibres in various processes after spinning, which troubles, in turn, cause yarn breakage, unevenness of the size of filament and other drawbacks. Generally, if copolyamide contains more than about 5% by weight of copolymerizable component, when the fibres are unwound from a bobbin or pirn in processes after spinning, tension irregularities occur due to the sticking and cohesion by fusion between said fibres, so that it is hardly possible to obtain homogeneous fibres free from yarn breakage and unevenness of the size of filament. For this reason,

in order to prevent above mentioned troubles, a copolyamide which contains a very small amount of copolymerizable component has been used in the production of the conventional highly shrinkable polyamide fibres. Further, since the conventional highly shrinkable polyamide fibres are produced generally by using copolyamide, they are considerably poor in heat resistance and light resistance as compared with the usual homopolyamide fibres, e.g., nylon-6, nylon-66, nylon-610 and nylonll. Furthermore, in case that titanium oxide or the like is added for the purpose of delustering in the polymerization of the copolyamide, the electrolytic property of the copolymerizable component causes the coagulation of the titanium oxide, with the result that the copolyamide thus obtained includes unevenly distributed titanium oxide particles which will cause troubles such as yarn break- 3,526,571 Patented Sept. 1, 1970 age and unevenness of the size of filament in various processes after spinning.

Accordingly, an object of the present invention is to eliminate these drawbacks as found in such conventional fibres and provide an extremely homogeneous and highly shrinkable polyamide fibre which is free from troubles such as unevenness of the size of filament and yarn breakage due to the sticking and cohesion by fusion between fibres in various processes after spinning in spite of the fact that use is made of a copolyamide which contains a large amount of copolymerizable component. Another object of the invention is to provide a highly shrinkable fibre which is excellent in heat resistance and light resistance as compared with the conventional highly shrinkable polyamide fibres.

The method according to the invention is characterized by the simultaneous melt spinning of copolyamide and homopolyamide through the same orifice in such a manner that the copolyamide component forms a core portion throughout the entire length of the unitary fibre and the homopolyamide having a substantially uniform thickness forms a sheath completely surrounding said copolyamide component, the thickness of the homopolyamide component being controlled so as to be 1-15% of the diameter of the unitary fibre.

For a better understanding of the invention reference is taken to the accompanying drawings, wherein FIG. 1 shows a vertical sectional View of a spinneret apparatus used in the production of fibres according to the invention; and

FIG. 2 shows an enlarged cross-sectional view of fibres obtained according to the invention.

Referring to FIG. 1, a spinneret 9 has an annular supply chamber 1 completely separated by an annular partition wall 13, and a cylindrical central supply chamber 2, these supply chambers 1 and 2 being provided at their bottoms with communication holes 3 and 6, respectively, leading to the lower part.

A nozzle plate 10 has a raised annular edge 12 and an annular groove 5 provided with orifices 8 at its bottom. The nozzle plate 10 is firmly pressed and fixed to the lower surface of the spinneret 9 at the surface of the raised edge 12 by a retainer ring 11. In this connection, the axis of introduction holes 4 projecting downwardly from the communication holes 3 are arranged so as to be perfectly aligned with the axis of the orifices 8. Further, a space chamber 7 is defined between the lower surface of the spinneret 9 and the nozzle plate 10.

In such apparatus, a molten copolyamide component A is supplied to the annular supply chamber 1 and a homopolyamide component B is supplied to the central supply chamber 2. The component A is extruded through the communication hole 3 into the annular groove 5. On the other hand, the component B flows through the communication hole 6 and the space chamber 7 into the annular groove 5 and surrounds the component A, and the component A surrounded by the component B is extruded through the associated spinning hole 8 to form such a fibre that the component A is surrounded concentrically by the component B.

A typical example of the fibre thus obtained is shown in enlarged cross-sectional view in FIG. 2.

As shown in FIG. 2, it is of the utmost importance to the fibres obtained according to the present invention that the component A is completely surrounded by the component B. If the component A should be exposed to the outside even though slightly, in such exposed areas not only objectionable phenomena such as sticking and cohesion by fusion but also irregularities in strength, elongation, light resistance, heat resistance and other properties would occur, thereby the quality of yarn is considerably decreased. Moreover, the thickness of the sheath, that is, component B should be substantially uniform over the total periphery portion and the total length of the fibre. For other special purposes, an attempt would be made to give maldistributed distortions in the filaments produced by spinning in such a manner that the introduction holes 4 of the above mentioned apparatus are positioned in eccentric relation to the orifices 8 so that the core portion and sheath may be arranged eccentrically. However, the method of the present invention does not aim crimpability as seen from the object, but aims production of a highly shrinkable fibre having no loops and crimps for particular applications, so that both of the components A and B should be concentrically arranged. If the component B should happen to have irregularities in thickness, this would give the possibility of developing loops and crimps during heat treatment or cause irregularities in the quantity of yarn, so it is not preferable.

According to the present invention, not only the apparatus of the type shown in FIG. 1 but also other types of spinning apparatuses can be used. It is, however, essential in every case to spin such a manner that the copolyamide component may be arranged in the core portion and the homopolyamide component may surround said copolyamide.

The thickness of the homopolyamide component which surrounds said copolyamide is preferably 1-15% of the diameter of the fibre. If the thickness of the homopolyamide component is less than 1% of the diameter of the fibre, such thickness is insufiicient for preventing various drawbacks of copolyamide component, so that there will be troubles such as sticking, unevenness of the size of filament, and yarn breakage as has been in the case of the conventional fibres, and, moreover, the resulting fibre will be extremely poor in heat resistance and light resistance. On the other hand, if it is more than 15% of the diameter of the fibre, this is also undesirable, since in this case the proportion occupied in the fibre by the copolyamide component decreases, so that the desired fibre having a high thermal shrinkability cannot be obtained, that is, the resulting fibre would have a shrinkability as poor as the conventional fibre. If the thickness of the homopolyamide falls within the above mentioned range, a fibre is more excellent in shrinkability, heat resistance and light resistance as compared with the conventional shrinkable fibre can easily be obtained.

The thickness of the homopolyamide component may be suitably selected depending upon the kind of the copolyamide employed and the uses of the fibres.

In order to restrict the thickness of the homopolyamide within the above mentioned range, the amounts of the components A and B supplied to the supply chambers 1 and 2 are controlled by a gear pump or the like so that the bonding ratio may be 24:1 to 49:51 when both of the components are conjugate spun.

The homopolyamides and copolyamides used in the present invention include various polyamide groups. For examples as the homopolyamides, mention may be made of nylon-6, nylon-66, nylon-610, nylon-7, nylon-11, nylon-12, polymetaxylene diammonium adiapte, polyparaxylene diammonium adipate and etc.

As the copolyamides, mentioned may be made of copolymer nylons obtained by the optional combination of two or more of such polyamide-forming substances as e-caprolactam, nylon-66 salt, nylon-610 salt, nylon-l2 salt, metaxylylene diammonium adipate, paraxylylene diammonium adipate, hexamethylene diammonium terephthalate, hexamethylene diammonium isophthalate and etc.

According to the present invention, a copolyamide which is a highly shrinkagle component is arranged in the core portion and a homopolyamide is arranged so as to surround said copolyamide component, whereby drawbacks such as sticking and cohession by fusion between fibres in various processes after spinning can be eliminated and moveover a highly shrinkable polyamide fibre which is excellent in light resistance and heat resistance can be obtained, so that the obtained fibre can be utilized in a very large field compared with the conventional fibres.

The following examples are given in illustration of this invention and are not intended as limitations thereof. The part in the examples means by weight.

EXAMPLE 1 A copolymer nylon (component A) having a relative viscosity of 2.6 measured in 98% sulphuric acid which was obtained by the copolymerization of parts of e-caprolactam and 25 parts of hexamethylene diammonium isophthalate (said copolymer nylon being hereinafter abbreviated to 6/6I), and nylon-6 (component B) having a relative viscosity of 2.7 were simultaneously spun through the same orifice at a conjugate ratio of 20:1 by using the apparatus shown in FIG. 1, and then the resulting 70 denier non-stretched fibre was Wound on a bobbin. A microscopic examination of the cross-section of this non-stretched fibre showed that the component B concentrically surrounded the component A and the thickness of the component B was about 1.3% of the diameter of the fibre. The non-stretched fibre was stretched to 4.2 times its original length at room temperature to obtain an extremely uniform stretch fibre without causing any trouble.

The shrinking percentage in hot water of the stretched fibre was excellent such as 41%. (Shrinking percentage in hot water here refers to a shrinking percentage measured after the material is immersed in boiling water for 10 minutes under a load of 0.5 g./d.). Further, in order to compare with the above mentioned sample, 6/61 (whose ratio by weight is /15) having a relative viscosity of 2.6 was spun solely, and the resulting fibre was stretched to 4.2 times into original length. However, the stretched fibre was partially stuck between the filaments, so that the filaments cannot easily be unwound from the bobbin and yarn breakage occurred between stretching rollers. Thus, a satisfactory stretched yarn could not be obtained.

A part of the obtained stretched fibre Was used to determine the shrinking percentage in hot water. It was found to be 34%.

EXAMPLE 2 To a molten mixture consisting of parts of caprolactam and 10 parts of a salt of m-xylylene diamine and adipic acid was added 0.4 part of adipic acid while stirring, and then the resulting mixture was copolymerized at a temperature of 80 C. for 8 hours to obtain a copolymer nylon having a relative viscosity of 2.4 (hereinafter abbreviated to 6/MXD-6).

The copolymer nylon (component A) and the nylon-6 (component B) used in Example 1 were melt-spun at the conjugate ratio of 5:1 by using the apparatus shown in FIG. 1 and then the resulting fibre was stretched to 4.2 times its original length to obtain a 15 denier unitary fibre (the fibre being referred to as Fibre 1).

Further, the 6/MXD-6 as obtained by the copolymerizing operation mentioned above and the nylon-6 were separately melt-spun and stretched to 4.2 times its original length to obtain 15 denier unitary fibres. (The unitary fibre obtained from the 6/MXD6 is referred to as Fibre 2 and the other obtained from the nylon-6 is referred to as Fibre 3.)

As to Fibres 1, 2 and 3, their shrinking percentage in hot water and the number of yarn breakage occurred until 1 kg. of stretched fibre was obtained were measured, and

their strength-preserving percentage after fibres were subjected to radiation from a fade-o-meter for 100 hours were measured. The results of these measurements are shown in Table 1.

TABLE 1 Fibre 1 Fibre 2 Fibre 3 Number of yarn breakage 2 11 0 Shrinking percentage in hot water, percent 28 32 12 Strength-preserving percentage, when not subjected to radiation, percent 100 100 100 Strength-preserving percentage, when subjected to radiation, percent 71 40 90 EXAMPLE 3 A copolymer nylon having a relative velocity of 2.4 (component A) obtained by the copolymerization of 70 parts of e-caprolactam and 30 parts of nylon-66 salt, and nylon-6 (component B) as used in Example 1 were meltspun in a conjugate ratio of 1:1 by using the apparatus shown in FIG. 1, and the resulting fibre was stretched to 4.2 times its original length at room temperature to obtain a 15 denier unitary fibre.

The thickness of the component B of this fibre was about 14.6% of the diameter of fibre, shrinking percentage in hot water being 23%.

Further, the above mentioned copolymer nylon was spun solely and then the resulting fibre was stretched at room temperature for trial. However, the fibre could not be stretched at all, since the sticking between the nonstretched spun fibres was very intense.

It is apparent that many variations may be made in the method and apparatus of this invention without departing from the spirit and scope thereof.

What I claim is:

1. A highly shrinkable polyamide filament having no stickiness between filaments which does not form loop and crimp by heating, which comprises a copolyamide core component extending the total length of the filament and a homopolyamide component having a substantially uniform thickness which forms a sheath completely surrounding the copolyamide component, the thickness of the sheath being 1 to 15% of the filament diameter, said homopolyamide being selected from the group consisting of polycapramide, polyhexamethylene adipamide, polyhexamethylene sebacamide, polyheptamide, polyundecamide, polydodecamide, polymetaxylylene adipamide and polyparaxylylene adipamide, and said copolyamide being a copolymer of two or more polyamide forming materials selected from the group consisting of e-caprolactam, hexamethylene diammonium adipate, hexamethylene diammonium sebacate, w-aminododecanoic acid, metaxylylene diammonium adipate, paraxylylene diammonium adipate, hexamethylene diammonium terephthalate and hexamethylene diammonium isophthalate.

2. A filament as defined in claim 1, wherein the amount of each copolymerisable component in the copolyamide is at least 5 weight percent.

3. A filament as defined in claim 1, wherein the thickness of the sheath is 1 to 4.5% of the filament diameter.

References Cited UNITED STATES PATENTS 3,118,011 1/1964 Breen. 3,271,837 9/1966 Au et al. 264-11 3,315,021 4/ 1967 Luzzatto.

FOREIGN PATENTS 830,441 3/1960 Great Britain.

972,932 1/1965 Great Britain.

981,003 1/1965 Great Britain. 1,422,393 11/1965 France.

DONALD J. ARNOLD, Primary Examiner J. H. WOO, Assistant Examiner US. Cl. X.R. 

